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Health and medicine
Course: Health and medicine > Unit 7
Lesson 1: Intro to endocrine hormones- Intro to the endocrine system
- Endocrine gland hormone review
- The hypothalamus and pituitary gland
- Hormone concentration metabolism and negative feedback
- Types of hormones
- Cellular mechanism of hormone action
- From terpenes to steroids part 1: Terpenes
- From terpenes to steroids part 2: Squalene, cholesterol, and steroids
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Types of hormones
There are three major types of hormones. 1) Protein hormones (or polypeptide hormones) are made of chains of amino acids. An example is ADH (antidiuretic hormone) which decreases blood pressure. 2) Steroid hormones are derived from lipids. Reproductive hormones like testosterone and estrogen are steroid hormones. 3) Amine hormones are derived from amino acids. Epinephrine, which helps regulate the fight-or-flight response, is an amine hormone. . Created by Ryan Scott Patton.
Want to join the conversation?
- At, Why proteins and polypeptides are charged? 2:33(9 votes)
- Amino acids are often charged. sometimes the overall charge is neutral despite individual charges in the amino acid (zwitterion), but often the overall charge is not neutral. As these amino acids are linked to form polypeptides, their charges interact. This results in the overall molecule being charged. For more info, check out a great playlist on the topic by Tracy here:
http://www.khanacademy.org/science/mcat/biomolecules/amino-acids-and-proteins1/v/central-dogma-molecular-biology(18 votes)
- Just a tip! In the description of this video, where the types of hormones have been mapped out, ADH (anti-diuretic hormone) is mentioned to decrease blood pressure. ADH works by helping the body to retain/reabsorb it's water content, therefore increasing the volume of fluid within the vessels. This would lead to an increase in blood pressure, not a decrease.(12 votes)
- Haha noticed that too. It's still in the description. Thanks for your post.(2 votes)
- AtRyan said that "all of our responses to the world around us are signaled by hormones." Aren't there quite a few processes that aren't signaled by hormones, like the way that most of the nervous system functions? 9:58(6 votes)
- Daniel, many neurotransmitters are also hormones! example Dopamine :)(14 votes)
- Explain why posterior pituitary hormone doesn't require releasing hormones.(1 vote)
- The posterior pituitary gland is simply an extension of the hypothalamus, it is heavily innervated by nerve endings that begin in the hypothalamus. So, since it's not entirely distinct from the hypothalamus, like the anterior pituitary gland is, it doesn't need releasing hormones.(7 votes)
- why do we have polypeptide hormones at all why cant all hormones be steroid hormones so they can cross the cell membrane without the help of a secondary messenger(2 votes)
- Because there are many things you can do by using secondary messengers. For starters, they are much faster than changing nuclear expression (which many steroid hormones do). Moreover, it allows for very complex interactions between many different signalling systems, multiple hormones converging, or secondary messengers diverging from the same hormone in different contexts. For specifics, read up downstream signalling of Calcium in nerves or muscles or a large variety of tissues, it often has multiple interactions with many signalling systems and hormones(5 votes)
- What are tropic hormones?(1 vote)
- Tropic hormones are hormones that have other endocrine glands as their target. Most tropic hormones are produced and secreted by the anterior pituitary.(5 votes)
- The way you explain polypeptides is kinda confusing: "many peptide bonds come together to form a polypeptide" also sounds wrong? You just mean that many peptide's bond to form polypeptides right? Thanks.(2 votes)
- Polypeptides are formed when many amino acids are bound together through the formation of peptide bonds.(3 votes)
- I may have missed it. What group do epinephrine and norepinephrine belong to? I believe they come from the adrenal cortex and many steroids come from there, right?(2 votes)
- Both Epinephrine (Epi) and norepinephrine (Norepi) are hormones secreted into blood by the adrenal medulla (not the cortex), where they serve as chemical mediators. Only Norepi is a neurotransmitter produced by the postganglionic neurons of the sympathetic sysytem.(3 votes)
- thanks this is so helpful .....(3 votes)
- What is the difference between neurotransmitters and hormones?(2 votes)
- hormones are secreted by the endocrine system and control multiple aspects of human growth and development and are secreted regularly, for example testosterone is produced i both males and females, but more so in males because of their testes. Neurotransmitters are chemicals released by the brain in the brain and transfer messages between neurons via synapse's and synaptic gaps. neurotransmitters are also short lived, unlike hormones which the body produces regularly, neurotransmitters may be released at random or in certain situations, i.e fight-or-flight.(2 votes)
Video transcript
OK. So when I introduced
the endocrine system, I mentioned that hormones
can be classified by where they function. And we talked about autocrine
function and paracrine function and endocrine function. But maybe even more
importantly, hormones can also be classified
by structure. And I say more importantly
because the structure of a hormone really
determines how it works. And so that's what I
want to talk about today, the three major
types of hormones. And the first major
type of hormones are proteins and polypeptides. And just as a refresher,
proteins and polypeptides are made up of amino acids. And these amino acids are linked
together with peptide bonds. And so many peptide
bonds come together to form a polypeptide
or a protein. And these proteins
and polypeptides form most of our
body's hormones. And these hormones can
range from small to large. And to give you an example
of what I mean by that, imagine it's three or so
amino acids linked together forming a hormone. That would be a
small polypeptide. In three amino
acids, we're talking about a handful of atoms,
maybe 20 or so atoms. And just as a
frame of reference, a cell in your
body, one cell, has on the order of a trillion
atoms just inside that one cell. And there are 100 trillion
cells in your body. And so we're talking about
very, very, very small things. And they can range from
these small collections of amino acids, all
the way to hundreds and hundreds of amino acids. So they can get quite large. And the break point
becomes right around 100. And that's where we
shift from calling them polypeptides to proteins. And just like all
proteins in your body that are going to be excreted,
proteins and polypeptides hormones are made in the
rough endoplasmic reticulum of the cell. And I'll shorten that to "RER." And they go from the rough
endoplasmic reticulum to the Golgi apparatus. And from the Golgi
apparatus, they're kind of repackaged into
vesicles that can eventually be excreted from the cell. And because proteins
and polypeptides are made of amino acids,
they're typically charged. Which makes them water
soluble, but it also gives them a really hard
time crossing cell membranes. And so typically
the receptors are located in or on a cell surface. And because the receptors are
located in or on a cell surface and these protein and
polypeptide hormones can't actually travel into
the cell, what they do is they initiate
a cascade effect of secondary messengers
inside the cell. And I'm going to
do an entire video about how that
signaling cascade using secondary messengers
actually works. But the main idea is that when
these protein and polypeptide hormones bind to
the cell surface, they initiate a response
inside the cell. And we refer to that as a
secondary messenger system. And so to save some
time, I went ahead and drew in an example
of a polypeptide hormone. And I'm going to kind
of fade it in for us. And I want to show
you on this drawing where the peptide bonds are
because these peptide bonds really pull this class
together and unify them. And so right in between
the carbon and the nitrogen here and the carbon
and the nitrogen here, I'll draw some arrows. These are the peptide bonds
that I was referring too, these carbon-nitrogen bonds. And so they can be small
and they can be large. But these links of
amino acids that are used as chemical messengers
to signal effects in the body are called proteins
and polypeptides. And one example is insulin. Insulin is a relatively
large hormone. And it's a protein hormone. OK. So we've got proteins
and polypeptides. And then the second major
type of hormones are steroids. And when we hear
steroids, I don't know, the first thought
that comes to my mind are a bunch of athletes
getting in trouble with their regulating
committees. But steroids are actually one
of the major types of hormones used in our body to communicate. And so there are a lot
of steroids in our body. But steroids come from lipids. And the major lipid that
these steroids come from is cholesterol. And because they come
from cholesterol, steroids have a really
characteristic structure that all of them share. And so I went ahead and
I predrew that as well. I'm going to fade that in. And so this is kind of
the characteristic steroid backbone. And so you can see there are
four ring structures here. And these rings are
made of carbon atoms. And so there are three
cyclohexane rings or six-membered carbon rings
and one cyclopentane ring. And I'm going to label
those A, B, C, and D. And what this
characteristic structure, comes a really characteristic
way of signaling a cell. And so unlike proteins and
polypeptides, whose receptors are on the cell
surface, steroids, because they're made of
lipids, have a really easy time passing through
the cell membrane. And their receptors are
located inside the cell. And so steroids usually
go all the way inside of the cell to signal the
receptor as primary messengers. They're actually
doing the signaling. And oftentime,
their receptors are located either in the cytoplasm
or all the way in the nucleus. But steroids typically
go in, and their effect goes all the way down to the
transcription and translation level of proteins. And so as primary messengers,
they're going inside the cell, and they're effecting a
change in that cell that's going to result in
the transcription and the translation
of new proteins and new products
inside the cell. And I'm going to do a video
on how these steroids actually affect the cell as well. But for now, I want
you to be thinking of steroids as one of the major
hormones that are in our body, not just a means
for athletes getting an edge on the competition. And so some examples of
big steroids in the body are those that come
from the adrenal cortex, like cortisol and aldosterone,
and those hormones that come from the gonads, like
the sex hormones, testosterone and estrogen and progesterone. And so we've got steroids. And we've got proteins
and polypeptides. And the third major type
of hormones by structure are tyrosine derivatives. And tyrosine derivatives come
from the amino acid tyrosine. And you might have
caught on that I said these come from tyrosine,
which is an amino acid. And I told you earlier that
protein and polypeptide hormones are made
of amino acids. And so you might
ask yourself, why do these get their own major
class if these are also made of an amino acid? And what makes them
really special, A, is that they're made
up of one amino acid. So one amino acid,
tyrosine, is manipulated to make these hormones. And B, these hormones that
are derived from tyrosine end up being able
to sometimes act like proteins and
polypeptides and sometimes act like steroids. So they really get
their own class. And an example of tyrosine
derivatives in the body are those that come from the
thyroid gland, like T3 and T4, or triiodothyronine
and thyroxine, that stimulate metabolism. And these tyrosine derivatives
act really similarly to steroids. And then another example
of tyrosine derivatives are catecholamines. And catecholamines
are those hormones that are produced in
the adrenal medulla that are involved in our fight
or flight responses, like epinephrine
and norepinephrine. And these thyrosine derivatives
act really similarly to peptides by binding on
the outside of the cell and releasing those secondary
messengers inside the cell. And so the thyroid hormones
that are tyrosine derivatives act like steroids. And the catecholamine
tyrosine derivatives act like proteins
and polypeptides. But it's important
to remember that they form their own unique
class because they're all derived from the
amino acid tyrosine. And because I did
it for proteins, and polypeptides, and
steroids, I went ahead and I drew in what
tyrosine looks like. So that's tyrosine. And that's the amino acid
that this class of hormones is derived from. And so I know it's
hard to make learning these types of hormones fun. But maybe at least we
can let our minds blow up a little bit over the
fact that the structure of these hormones dictates
almost everything we think or do, from fear, to hunger, to
urinating, and pushing babies out. All of our responses
to the world around us are signaled by hormones.